Double-grid-tube transmitter



July 15, 1930. JQBST ET AL 1,770,486

DOUBLE GRID TUBE TRANSMITTER Filed Feb. 6, 1928 INVENTOR GUNTHERJOBST BY ANS R0 R TORNEY cuit of the protective grid.

Patented 15,1930

O F C GUNTEER JOIBS'I. AND nA vs RODER, en ma,- G RM NY, assrenonswro ensurin- SCHAFT mm DRAHTLOSE rnrnennrnmn; -13. n. -n'A nscHEs, or BERLI ean- MANY, A CORPORATION or GERMANY w "noun L -eR n-T BE-,a:im vsiair'riaa.

Application filed February 6,1928, s rial Na :The subject matter ofthepresent inven tion is an arrangement for telephony and telegraphy circuits for valve or tube trans-- 'mitters. 4

' trio waves may be effected in a self excited or a separately excited double gridtube, im-'- pressing modulatingv potentials upon' the anode screening grid. f I

In the circuit arrangements heretofore most commonly used, the inconvenience is often met that during the periods when this gridis subject to the action of positive otential, disturbing influences of the secondary electron current issuing from the space charge grid manifest themselves, and that furthermore a grid current flows in thecir- According to-th'e disclosures of the present invention, an arrangement is used in which this objectionable feature is eliminated by maintaining the. total potential at the anode screening grid always negative during the transmission of signals. One'method of v arriving at this result is to use only the negative half cycles of the oscillations. used for the transmission of signals. A more practical scheme is to apply-a negative biasing po- 'tential to the anode screening grid, the value.

of said biasing potential being chosena great enough-value so that the total potential will remain permanently negative. An arrangement according to which Fig. 1 represents-one preferred bodiment of our invention, and.

Fig. 2, shows curves explaining the what,

, tion of the circuit shown'in Fig. 1.

As will be seen from Fig; 1, a thermionic 6.. Inserted in this grid circuit is a battery It is well known'thatfinodulation ofelecthe presentinvention is illustrated in the. drawings -1n 252,182, and in -Germany February 26, 1927.

Twlhose potential is so chosen that the total resulting potential at the grid 3 remainsalways negative.

is shown in Fig. 2 by curve 8. The total po- The shape of the potential the grid 3 I tent'ial ata-ny instant, consistsof the potential 'E of the battery I), .plus the instantaneous impressed alternating CHII'BHt POtGII- tial of the generator 5. As will be seen from the graph,'the size of the battery potential must be so selected that it willbe higher than the greatest amplitude E of the alternating 'current potential so that no possibility of the grid ev'e'rbecoming positive will occur.

In Fig. 2, curve 9 shows theimpressed voltage-due tothe generator 5, while the line 10 shows the battery 7 negative potential upon the grid; Adding these two curves alge- 'braically,curve 8 will be obtained from which the true condition of the grid will be evident.

' While we have indicated. and described one I arrangement for carrying our invention into described, but that many modifications may be employed without departing from the slope of our invention asset forthin the ap ended claims.

, a'vin thus described our invention what we desire to protect by Letters Patent is as follows:

1-. In a transmitter circuit, double grid tube circuit comprising a space charge grid circuit and an anode screening grid circuit, means comprising a source of high frequency currents and a condenseninseries with said space charge grid and conductively associated therewith for generating oscillationsin said transmitter, modulating means for said anode screening grid, and means for main: taining the total potential at said last named grid at a negative value.

2. YA transmitter circuit comprising a' dou-' ble grid tube having a space charge grid circuit, an oscillation generatin means and a condenser in series conductiv y connected in said last named circuit, a resistance shunted across said condenser, a modulating grid circuit, and means comprising a source of potential in said last named circuit for mamtaining the total grid potential of said tube at a negative value.

' GUNTHER JOBST.

HANS RODER. 

